Organic light emitting display device and apparatus

ABSTRACT

Embodiment of the present disclosure discloses an organic light emitting display device and apparatus, the organic light emitting display device includes a first electrode and a second electrode disposed opposite to each other, a light emitting layer positioned between the first electrode and the second electrode, and a cap layer positioned on a side surface of the second electrode facing away from the light emitting layer, wherein the cap layer includes at least two composite layers, the refractive index of the composite layer of the at least two composite layers closer to the second electrode is greater than that of the other composite layer further away from the second electrode in the range of wavelength of 400 nm to 700 nm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to a Chinese patent application No.20161127161.4 filed on Dec. 30, 2016 and titled “Organic Light EmittingDisplay Device and Apparatus”, which is incorporated herein by referencein its entirety.

TECHNICAL FIELD

Embodiments of the present disclosure relate to an organic lightemitting display technology, and more particularly, to an organic lightemitting display device and apparatus.

BACKGROUND

An organic light-emitting display (OLED) device is a thin filmlight-emitting device made of organic semiconductor material and drivenby direct current voltage, which has the characteristics of lightness,large viewing angle and power saving. With the commercializedapplication and development of the display devices, requirements of apixel fineness and a light extraction efficiency of the OLED devicerequired by the commercialized products are increasingly higher. Inorder to improve the light extraction efficiency, the existing OLEDdevices usually utilize a top-emitting mode.

A top-emitting OLED device of the prior art is illustrated in FIG. 1.The OLED device includes a substrate 10, an anode 11, a hole transportlayer 12, a light emitting layer 13, an electron transport layer 14, acathode 15, and a cap layer 16, and the light is emitted from the top ofthe device. Specifically, the constituent materials of the electrontransport layer 14 is an organic material doped with LiQ; theconstituent materials of the cathode 15 is an alloy of Mg and Ag; andthe constituent materials of the cap layer 16 is an organic material.

In the existing organic light emitting display device, the cap layer ismade of the organic material, which has the effects of high refractiveindex and high light extraction efficiency, but the color castphenomenon is serious.

SUMMARY

An embodiment of the present disclosure provides an organic lightemitting display device and apparatus to improve the color castphenomenon of the organic light emitting display device.

An aspect of an embodiment of the present disclosure provides an organiclight emitting display device, which includes:

a first electrode and a second electrode disposed opposite to eachother, a light emitting layer positioned between the first electrode andthe second electrode; and

a cap layer positioned on a side surface of the second electrode facingaway from the light emitting layer, the cap layer includes at least twocomposite layers, the refractive index of the composite layer of the atleast two composite layers closer to the second electrode is greaterthan that of the other composite layer further away from the secondelectrode in the range of wavelength of 400 nm to 700 nm.

Another aspect of an embodiment of the present disclosure furtherprovides an organic light emitting display apparatus including theorganic light emitting display device as described above.

According to the organic light emitting display device and apparatusprovided by the embodiments of the present disclosure, the cap layerincludes at least two composite layers, the refractive index of thecomposite layer of the at least two composite layers closer to thesecond electrode is greater than that of the other composite layerfurther away from the second electrode, in the range of wavelength of400 nm to 700 nm. In the embodiment of the present disclosure, therefractive index of the composite layer in the cap layer closer to thesecond electrode is relatively larger, and the light reflection effectcan be reduced, thereby improving the light extraction efficiency of thedevice. The refractive index of the other composite layer in the caplayer further away from the second electrode is relatively smaller, anda certain reflection phenomenon may occur during propagation of lightfrom the composite layer closer to the second electrode to the othercomposite layer further away from the second electrode, such that theemission angle of the light is increased and the light is scattered indifferent directions to reduce the color cast phenomenon. Therefore, thecolor cast is mitigated by virtue of the cap layer while the higherlight extraction efficiency of the device can be ensured.

BRIEF DESCRIPTION OF DRAWINGS

In order to more clearly illustrate the embodiments of the presentdisclosure or the technical solutions in the prior art, the accompanyingdrawings, which are intended to be used in the description of theembodiments or the prior art, are briefly described as below, and itwill be apparent that the drawings in the following descriptions aresome embodiments of the present disclosure, and other drawings may beobtained by those skilled in the art according to these drawings withoutpaying any inventive work.

FIG. 1 is a schematic view of a top-emitting OLED device according tothe prior art;

FIG. 2 is a schematic view of an organic light emitting display deviceaccording to an embodiment of the present disclosure;

FIG. 3 is a schematic view of an organic light emitting display deviceaccording to an embodiment of the present disclosure;

FIG. 4 is a schematic view of another organic light emitting displaydevice according to an embodiment of the present disclosure;

FIGS. 5A to 5C are schematic views of a plurality of organic lightemitting display devices according to another embodiment of the presentdisclosure;

FIG. 6 is a schematic view of another organic light emitting displaydevice according to another embodiment of the present disclosure;

FIG. 7 is a schematic view of yet another organic light emitting displaydevice according to another embodiment of the present disclosure;

FIG. 8 is a schematic view of still another organic light emittingdisplay device according to another embodiment of the presentdisclosure; and

FIG. 9 is a schematic view of still another organic light emittingdisplay apparatus according to another embodiment of the presentdisclosure.

DETAILED DESCRIPTION

The technical solution provided by the present disclosure will beclearly described below by way of embodiments thoroughly, with referenceto the accompanying drawings of the embodiments of the presentdisclosure, in order to make the objects, technical solutions and theadvantages of the present disclosure clearer. It is apparent that theembodiments described are a portion of the embodiments of the presentinvention, but not all of the embodiments. All other embodimentsobtained by those of ordinary skill in the art without paying anycreative work are within the scope of the present disclosure, based onthe embodiments of the present disclosure.

FIG. 2 is a schematic view of an organic light emitting display deviceaccording to an embodiment of the present disclosure. The organic lightemitting display device includes a first substrate 170 and an uppersubstrate, a TFT array positioned between the first substrate 170 andthe upper substrate, an anode 110A, a light emitting layer 130Rcorresponding to an R pixel region, a light emitting layer 130Gcorresponding to a G pixel region, a light emitting layer 130Bcorresponding to a B pixel region, a cathode 120A, and a cap layer 140.The organic light emitting display device is a top-emitting OLED, inwhich a microcavity structure is formed between the anode 110A and thecathode 120A. The luminous mechanism of the organic light emittingdisplay device is such that, in the case of emitting a red light, apositive voltage is applied to the anode 110A corresponding to the Rpixel region and a negative voltage is applied to the cathode 120A, andthe holes generated by the anode 110A are injected into thecorresponding light emission layer 130R, the electrons generated by thecathode 120A are also injected into the corresponding light emittinglayer 130R; the electrons and holes that are injected into the lightemitting layer 130R are recombined to generate excitons, and radiationtransition of the excitons causes the light emitting layer 130R to emitthe red light.

In order to clearly describe the technical solution of the presentdisclosure, only the partial structure of the organic light emittingdisplay device is described and illustrated in the following embodimentsas an example.

FIG. 3 is a schematic view of an organic light emitting display deviceaccording to one embodiment of the present disclosure. The organic lightemitting display device includes a first electrode 110 and a secondelectrode 120 disposed opposite to each other, a light emitting layer130 positioned between the first electrode 110 and the second electrode120, and a cap layer 140 located at a side surface of the secondelectrode 120 facing away from the light emitting layer 130. The caplayer 140 includes at least two composite layers 141, in which therefractive index of the composite layer 141 of the at least twocomposite layers 141 closer to the second electrode 120 is greater thanthat of the other composite layer 141 further away from the secondelectrode 120 in the range of wavelength of 400 nm to 700 nm.

In the present embodiment, the optional organic light emitting displaydevice is a top-emitting display device, and the light is emitted from aside at the second electrode 120. The first electrode 110 and the secondelectrode 120 constitute a microcavity structure of the organic lightemitting display device, and the microcavity structure has a microcavityeffect. The organic light emitting display device includes the cap layer140 which can be used to adjust the length of the microcavity andthereby affecting the microcavity effect. Specifically, the cap layer140 is actually formed on a side surface of the cathode 120A facing awayfrom the first substrate 170 in the organic light emitting displaydevice shown in FIG. 2.

In the present embodiment, the cap layer 140 includes at least twocomposite layers 141. That is, the cap layer 140 is a multi-layerstructure, and the refractive index of the composite layer 141 of the atleast two composite layers 141 closer to the second electrode 120 isgreater than that of the other composite layer 141 further away from thesecond electrode 120 in the range of wavelength of 400 nm to 700 nm. Inthe this embodiment, the refractive index of the composite layer 141closer to the second electrode 120 is relatively large, then the lightreflection effect can be reduced, thereby improving the light extractionefficiency of the device. The refractive index of the composite layer141 further away from the second electrode 120 is relatively small, andthe process which the light is propagated from the composite layer 141closer to the second electrode 120 to the other composite layer 141further away from the second electrode 120 is a process which the lightis ropagated from the optical dense medium to the optical sparse medium.

It is known that when the light is propagated from the optical densemedium to the optical sparse medium, reflection occurs at an interfacebetween the light dense medium and the optical sparse medium. Therefore,in the present embodiment, a certain reflection occurs at an interfacebetween the composite layer 141 closer to the second electrode 120 andthe other composite layer 141 further away from the second electrode120, further the emission angle of light is increased and the light isscattered in different directions, thereby reducing the color castphenomenon.

It will be understood by those skilled in the art that the cap layer canimprove the light extraction efficiency, the refractive index differencebetween any two materials of the cap layer is relatively small, but theconstituent materials of the composite layer of the cap layer in thepresent disclosure is any of existing known material for the cap layer.Therefore, the refractive index of the composite layer closer to thesecond electrode is considerably greater than that of the othercomposite layer further away from the second electrode in the presentdisclosure, but the refractive index difference is not very large basedon the fact that they both are materials for the cap layer. Accordingly,a partial reflection of the light, rather than a full reflection of thelight, occurs at the interface between the composite layer closer to thesecond electrode and the other composite layer further away from thesecond electrode, and the reflection will slightly reduce the lightextraction efficiency of the device, whereas the composite layer closerto the second electrode can improve the light extraction efficiency. Asa result, the light extraction efficiency improved by virtue of the highrefractive index of the composite layer closer to the second electrodecan compensate for the reduction of the light extraction efficiencycaused by the reflection, thereby ensuring that the device has a higherlight extraction efficiency.

In view of the above, the cap layer provided in the present embodimentalso reduces the color cast phenomenon on the basis of ensuring a higherlight extraction efficiency of the device.

By way of example, on the basis of the above-described technicalsolution, the constituent materials of the second electrode 120 includesa metal material or a metal alloy material, and the constituentmaterials of the first electrode 110 includes indium tin oxide (ITO) orindium zinc oxide (IZO). The constituent materials of the firstelectrode and the second electrode also include other materials.Specifically, the first electrode also includes silver, so the firstelectrode may serve as a reflective film layer so that the light istotally reflected on the first electrode. Specifically, the firstelectrode may act as the anode of the organic light emitting displaydevice, thus the light may be totally reflected on the first electrode.The second electrode may act as the cathode of the organic lightemitting display device, thus the light is emitted through the secondelectrode, so the thickness of the second electrode is very thin. Itwill be understood by those skilled in the art that the constituentmaterials of the first electrode and the second electrode are various,including but not limited to the above examples, and the relevantpractitioners may select the constituent materials forming the firstelectrode and the second electrode according to requirements forproducts by themselves. The constituent materials is not limitedspecifically in the present disclosure. The constituent materials of thesecond electrode may be selected to include, for example, any one ofsilver alloy with magnesium, silver metal, silver ytterbium alloy andsilver rare earth metal alloy. In other embodiments, the constituentmaterials of the second electrode may also be selected to include indiumtin oxide (ITO) or indium zinc oxide (IZO), and the constituentmaterials of the first electrode includes a metal material or a metalalloy material.

Optionally, the metallic material is silver, and the metal alloymaterial is a silver alloy having a silver content of more than 90%. Inthe prior art, the cathode of the organic light emitting display deviceis made of magnesium silver alloy, Mg:Ag=9:1 or 10:1, in which the highdegree of activity of the magnesium causes the cathode to be susceptibleto water and oxygen to fail. In addition, the transmittance of magnesiumis poor, resulting in the cathode transmittance is not high, therebyaffecting the light efficiency of device. In the present embodiment, theconstituent materials of the second electrode 120 is silver or a silveralloy having a silver content of more than 90%. Because thetransmittance of silver is very high, and the silver having a high massratio is used in the second electrode 120, the transmittance of thesecond electrode 120 is high, and thus the light extraction efficiencyof the organic light emitting display device can be improved.Specifically, the combination of the second electrode 120 and the caplayer 140 have a transmittance greater than 65%. In addition, the lowdegree of activity of silver facilitates the improvement of thestability of the device.

On the basis of the exemplary embodiment as described above, the lightemitting layer 130 includes a plurality of light emitting regions whichemit at least one color of light or only emit white light. When theplurality of light emitting regions emit the at least one color oflight, the organic light emitting material used in the light emittingregion corresponding to the different light emission colors of the lightemitting layer 130 is different. When the plurality of light emittingregions emit the white light, the organic light emitting material usedin the light emitting regions corresponding to the different lightemission colors of the light emitting layer 130 may be the same. Whenthe plurality of light emitting regions emit the white light, aplurality of color filter films respectively corresponding to theplurality of light emitting regions are arranged on the light emittinglayer 130 of the organic light emitting display device, and theplurality of color filter films include at least one of a red R filterfilm, a green G filter film, and a blue B filter film.

It will be understood by those skilled in the art that the structureillustrated in this embodiment is only a partial structure of theorganic light emitting display device, but the organic light emittingdisplay device also includes other structures such as a thin filmtransistor array substrate, a color film substrate, or a thin filmencapsulation layer. When a color filter film is arranged in the organiclight emitting display device, the color filter film may be produced ata plurality of positions, for example, directly on the cap layer or onthe color film substrate. In the present disclosure, the position atwhich the color filter film is produced is not limited specifically.

By way of example, the optional cap layer 140 has a thickness greaterthan or equal to 50 nm and less than or equal to 90 nm. When thethickness of the cap layer 140 is too thick or too thin, the lightoutput characteristics of the cap layer 140 would be affected. It willbe understood by those skilled in the art that the thickness of the caplayer is not limited to the above-described thickness range and that therelevant practitioners can set the thickness of the cap layer accordingto the requirements for products in actual production by themselves.

By way of example, the optional cap layer 140 includes any one orcombination of an organic material and an inorganic material. When thecap layer 140 is made of the organic material, since the organicmaterial has a higher refractive index, the light reflection phenomenonis reduced, and thus the light extraction efficiency of the device ishigher. When the cap layer 140 is made of the inorganic material, thecolor cast phenomenon of the device can be reduced. Accordingly, the caplayer 140 may be formed by laminating the organic material film layerand the inorganic material film layer.

As an example, the optional cap layer 140, as shown in FIG. 4, includesa first composite layer 140 a and a second composite layer 140 b whichare stacked in turn, where the first composite layer 140 a is in directcontact with the second electrode 120, and a refractive index of thefirst composite layer 140 a is greater than 1.8 in the wavelength rangeof 400 nm to 700 nm, and a refractive index of the second compositelayer 140 b is less than 1.7 in the wavelength range of 400 nm to 700nm. According to the present embodiment, the refractive index of thefirst composite layer 140 a in direct contact with the second electrode120 is relatively large, so the light reflection effect can be reduced,thereby improving the light extraction efficiency of the device. Therefractive index of the second composite layer 140 b is relativelysmall, so the light is transmitted from the first composite layer 140 ato the second composite layer 140 b. That is, the light propagates fromthe optical dense medium to the optical sparse medium. Therefore, acertain reflection of light occurs at the interface between the firstcomposite layer 140 a and the second composite Layer 140 b. Thus, thelight emission angle increases, and the light is scattered in differentdirections, thereby reducing the color cast phenomenon. In this way, thecolor cast phenomenon is improved on the basis that the light extractionefficiency of the device is ensured.

The thickness of the optional first composite layer 140 a is 50 nm, andthe thickness of the second composite layer 140 b is 20 nm. The higherrefractive index of the first composite layer 140 a can improve thelight extraction efficiency, and the relatively low refractive index ofthe second composite layer 140 b can improve the color cast phenomenon,and the light can be reflected at the interface between the firstcomposite layer 140 a and the second composite layer 140 b. It is knownthat a reflection can reduce the light extraction efficiency. In orderto ensure the higher light extraction efficiency and reduce the colorcast phenomenon of the device, it is preferable that the thickness ofthe first composite layer 140 a is greater than that of the secondcomposite layer 140 b. Specifically, the thickness of the firstcomposite layer 140 a is 50 nm, and the thickness of the secondcomposite layer 140 b is 20 nm. The thicker first composite layer 140 acan ensure that the device has a higher light extraction efficiencywhile the thinner second composite layer 140 b can reduce the color castphenomenon.

The optional first composite layer 140 a is made of 8-hydroxyquinolinealuminum, and the second composite layer 140 b is made of lithiumfluoride. The refractive index of the 8-hydroxyquinoline aluminum ishigher than 1.8, and the refractive index of the lithium fluoride isabout 1.3 to 1.4. The refractive index difference between the firstcomposite layer 140 a and the second composite layer 140 b is less, sothe reflection at the interface between the first composite layer 140 aand the second composite layer 140 b is less, thus the high refractiveindex of the first composite layer 140 a can improve the lightextraction efficiency, meanwhile the low refractive index of the secondcomposite layer 140 b can improve the color cast phenomenon.

In the organic light emitting display device according to the presentembodiment, the cap layer includes at least two composite layers, therefractive index of the composite layers of the at least two compositelayers closer to the second electrode is greater than that of the othercomposite layer of the at least two composite layers further away fromthe second electrode in a wavelength range of 400 nm to 700 nm. In thepresent embodiment, the refractive index of the composite layer closerto the second electrode in the cap layer is relatively large, so thatthe light reflection effect can be reduced, and then the lightextraction efficiency of the device can be improved, while therefractive index of the composite layer further away from the secondelectrode in the cap layer is relatively small, such that a certainlight reflection phenomenon may occur during the propagation of lightfrom the composite layer closer to the second electrode to the compositelayer further away from the second electrode, and then the emissionangle of the light is increased and the light is scattered in differentdirections, thereby reducing the color cast phenomenon. As such, the caplayer reduces the color cast phenomenon while ensuring that the devicehas a higher light extraction efficiency.

Another embodiment of the present invention provides an organic lightemitting display device which differs from any of the embodimentsdescribed above in that, as shown in FIG. 5A, it further includes afirst functional layer 150 with at least an electron transport layer 150a. The electron transport layer 150 a is located on a side surface ofthe second electrode 120 facing the light emitting layer 130. Arefractive index of the electron transport layer 150 a is less than 1.7in the wavelength range of 400 nm to 700 nm, and the thickness of theelectron transport layer 150 a is greater than or equal to 30 nm andless than or equal to 40 nm.

In the present embodiment, the first functional layer 150 is locatedbetween the light emitting layer 130 and the second electrode 120, andthe first functional layer 150 includes at least an electron transportlayer 150 a. The first functional layer 150 is used to enhance theability that electron of the second electrode 120 is injected andtransported to the light emitting layer 130, thereby balancing theinjection and transport of carriers and improving the carrierrecombination efficiency. In the present embodiment, since therefractive index of the electron transport layer 150 a is less than 1.7in the wavelength range of 400 nm to 700 nm, when the electron transportlayer 150 a having a lower refractive index is matched with the cathode,the light transmittance can be increased, and brightness and lightextraction efficiency of the device can be improved.

By way of example, on the basis of the above-described technicalsolution, the optional electron transport layer 150 a includes anelectron transporting material doped with a first guest material. Thefirst guest material includes at least an alkali metal, an alkalineearth metal and a rare earth metal. The electron transport materialincludes any one of an o-phenanthroline derivative or a substitutedproduct thereof, and a bipyridine derivative or a substituted productthereof.

According to the present embodiment, the electron transport materialincludes any one of the o-phenanthroline derivative or a substitutedproduct thereof, and the bipyridine derivative or a substituted productthereof, which have the advantage that the refractive index is lower.The refractive index of the electron transport layer formed by theexisting electron transport material is large, and when the light ispropagated from the electron transport layer to the cathode, since therefractive index of the cathode is smaller, the refractive indexdifference between the electron transport layer and the cathode islarge, thus the t reflection phenomenon will be caused at the interfacebetween the electron transport layer and the cathode, thereby affectingthe light extraction efficiency of device. The electron transport layer150 a formed by the electron transport material in the presentembodiment has a smaller refractive index and is in contact with thesecond electrode 120. When the light propagates from the electrontransport layer 150 a toward the second electrode 120, the refractiveindex difference between the electron transport layer 150 a and thesecond electrode 120 is small, and the light reflection phenomenon atthe interface between the electron transport layer 150 a and the secondelectrode 120 is weakened, thereby improving the light extractionefficiency of the device.

In the present embodiment, since the electron transport material isdoped with the first guest material, the refractive index of theelectron transport layer 150 a can be further reduced, and then thelight extraction efficiency can be further improved. The first guestmaterial is metal material, and when the electron transport layer 150 ais matched with the cathode, the first guest material in the electrontransport layer 150 a is capable of increasing the electron injectionrate of the cathode. In the present embodiment, the first guest materialis an active metal material. With the active metal being doped into theelectron transport material, it is possible to improve the electricalconductivity of the electron transport layer 150 a, that is to increasethe electron mobility of the electron transport layer 150 a, therebyreducing the light emitting voltage of the light emitting layer 130 andreducing the power consumption.

It is preferable that the electron transporting material is ano-phenanthroline derivative and the first guest material is Yb in thepresent embodiment. It will be understood by those skilled in the artthat the electron transporting material of the electron transport layerand the first guest material include, but are not limited to, the aboveexamples, and are not particularly limited in the present disclosure.

The content of the first guest material in the optional electrontransport layer 150 a is greater than or equal to 5% and less than orequal to 95%. When the content of the first guest material in theelectron transport layer 150 a is different, the electron mobility andthe enhancement rate of electron injection and transport exhibited bythe electron transport layer 150 a are also different. Therefore, oneskilled in the art can control the content of the first guest materialin the electron transport layer in accordance with the requirements forproducts by themselves. The content of the first guest material is notparticularly limited in the present disclosure.

Alternatively, as shown in FIG. 5B, the first functional layer 150further includes a hole blocking layer 150 b located on a side surfaceof the electron transport layer 150 a facing the light emitting layer130, and the thickness of the hole blocking layer 150 b is in the rangeof 5 nm to 30 nm. The difference in energy level between the electrontransport layer 150 a and the light emitting layer 130 is relativelylarge, which is not conducive to the electron transport. Therefore, thehole blocking layer 150 b may be arranged between the electron transportlayer 150 a and the light emitting layer 130, and the energy level ofthe hole blocking layer 150 b lies between the electron transport layer150 a and the light emitting layer 130, which minimizes the energy levelbarrier crossed when an electron transition takes place to enhance anefficiency of the electron injection and transport efficiency. It ispreferable that the hole transport layer 150 b is arranged between theelectron transport layer 150 a and the light emitting layer 130 when thecontent of the first guest material exceeds 25%.

In addition, the hole blocking layer 150 b can also block the hole ofthe light emitting layer 130 from being transferred to the secondelectrode 120, that is, the hole blocking layer 150 b is capable ofrestricting the holes in the light emitting layer 130 to improve theexciton recombination efficiency. It will be appreciated by thoseskilled in the art that the first functional layer may further includean electron injection layer and so on in other alternative embodiments,which is not only for improving the electron injection and transportcapabilities, but also for minimizing the energy level barrier crossedwhen the electron transition takes place.

Optionally, the electron transport layer 150 a includes at least a firstelectron transport layer and a second electron transport layer stackedin turn, as illustrated in FIG. 5C, and the second electron transportlayer is positioned on the side surface of the second electrode 120facing the light emitting layer 130. In the present embodiment, theelectron transport layer 150 a has a multi-film layer structure, so theeffect for flexibly adjusting the refractive index of the electrontransport layer 150 a can be achieved by adjusting the different filmlayers. For example, the doping content of the first guest material inthe different film layers may be adjusted such that the electrontransport layer 150 a has a desired refractive index parameter. Thethickness of the optional first electron transport layer is 15 nm andthe thickness of the second electron transport layer is 20 nm.

Another embodiment of the present disclosure also provides anotherorganic light emitting display device which differs from any of theembodiments described above in that, as shown in FIG. 6, it furtherincludes a second functional layer 160 located on a side surface of thefirst electrode 110 facing the light emitting layer 130, where thesecond functional layer 160 includes at least a hole transport layer 160a.

In the present embodiment, the second functional layer 160 is locatedbetween the first electrode 110 and the light emitting layer 130, andthe second functional layer 160 includes at least a hole transport layer160 a. The second functional layer 160 is used to enhance the abilitythat the hole of the first electrode 110 is injected and transported tothe light emitting layer 130, thereby capable of balancing the injectionand transport of the carriers and improving the carrier recombinationefficiency. It will be appreciated by those skilled in the art that thesecond functional layer in other alternative embodiments may furtherinclude at least one of a hole injection layer and an electron blockinglayer, so the second functional layer can not only improve the abilityof the hole injection and transport, but also minimize the energy levelbarrier crossed when the hole transition takes place.

It will be understood by those skilled in the art that the constituentmaterials of the hole transport layer of the present disclosure includesany known hole transporting material, which is not particularly limitedin the present disclosure.

Another embodiment of the present disclosure also provides an organiclight emitting display device which differs from any of the aboveembodiments in that, as shown in FIG. 7, it further includes the firstfunctional layer 150 and the second functional layer 160. The firstfunctional layer 150 is located between the light emitting layer 130 andthe second electrode 120, and includes at least an electron transportlayer 150 a, the second functional layer 160 is located between thefirst electrode 110 and the light emitting layer 130, and includes atleast a hole transport layer 160 a. As the first functional layer 150and the second functional layer 160 are arranged in the organic lightemitting display device, not only the injection and input capability ofthe electrons and the holes can be improved, but also the barrierobstacle occurred during the transition of the electrons and the holescan be reduced. The structure and function of the first functional layerand the second functional layer can be understood by those skilled inthe art, and the detailed descriptions thereof are omitted here.

Another embodiment of the present disclosure further provides stillanother organic light emitting display device which differs from any ofthe above embodiments in that, as shown in FIG. 8, it further includes afirst substrate 170 located on a side surface of the first electrode 110facing away from the light emitting layer 130, the first substrate 170is a rigid substrate or a flexible substrate.

In the present embodiment, the first substrate 170 may be selected asthe flexible substrate and encapsulated by using a thin filmencapsulation layer, and the corresponding organic light emittingdisplay device is a flexible organic light emitting display devicehaving a lower power consumption and a bendable property, which issuitable for a variety of display devices, especially for wearabledisplay devices. The material of the optional flexible substrate in thisembodiment is a polyimide or polyethylene terephthalate resin. It willbe understood by those skilled in the art that the material of theflexible substrate includes, but is not limited to, the above materials.Any material that can be utilized for the flexible substrate fallswithin the protection scope of the present disclosure. It will beappreciated by those skilled in the art that the first substrateincludes, but is not limited to, the flexible substrate. In otheralternative embodiments, the first substrate may be selected as therigid substrate and encapsulated by a thin film encapsulation layer or acover package, and accordingly a rigid organic light emitting displaydevice is provided. The organic light emitting display device has a widerange of field of applications and will not be described or explained indetail in the present disclosure. Relevant practitioners can choose thematerial of the first substrate according to the requirements forproducts by themselves.

In order to clearly demonstrate the technical solution of the embodimentof the present disclosure, a further embodiment of the presentdisclosure provides an organic light emitting display device whichincludes an anode, a buffer layer, a hole transport layer, a lightemitting layer, an electron transport layer (ETL), a cathode and a caplayer.

The anode is ITO, the thickness of the buffer layer is 10 nm, thethickness of the hole transport layer is 115 nm, the light emittinglayer is a blue light emitting layer and has a thickness of 25 nm, thethickness of the electron transport layer is 30 nm, the material of thecathode is silver and its thickness is 15 nm, and the thickness of thecap layer is 70 nm.

Specifically, the difference between the various organic light emittingdevices only lies in the following aspects.

The refractive index of the electron transport layer of the firstorganic light emitting display device Q1 is 1.72 at a wavelength of 550nm; the refractive index of the electron transport layer of the secondorganic light emitting display device Q2 is 1.5 at a wavelength of 550nm; and the refractive index of the electron transport layer of thethird organic light emitting display device Q3 is 1.3 at a wavelength of550 nm.

After optical tests, optical performances of Q1-Q3 are shown in Table 1below:

Refractive index Increased value Color cast of of ETL@550 of brightnessperspective@60° Q1 1.72 100% 100% Q2 1.5 103% 85% Q3 1.3 107% 70%

Taking the organic light emitting display device as indicated by Q1 as acomparison example, the refractive index of Q2 is less than the one ofQ1, the increased value of brightness of Q2 is 103% of the brightnessvalue of Q1, and the color cast of Q2 is 85% of the color cast value ofQ1. It is clear that Q2 has a higher brightness and less color cast.Namely, the display effect of the organic light emitting display deviceas indicated by Q2 is better.

Taking the organic light emitting display device as indicated by Q1 as acomparison example, the refractive index of Q3 is less than the one ofQ1, the increased value of brightness of Q3 is 107% of the brightnessvalue of Q1, and the color cast of Q3 is 70% of the color cast value ofQ1. It is clear that Q3 has a higher brightness and less color cast.Namely, the display effect of the organic light emitting display deviceas indicated by Q3 is better.

The refractive index of Q3 is less than that of Q2.

It can be seen that, it is possible to increase the brightness of thedevice and reduce the color cast by way of reducing the refractive indexof the electron transport layer so that the effects of improving thelight extraction efficiency of the device and reducing the color castcan be achieved.

A further embodiment of the present disclosure provides another organiclight emitting display device which includes an anode, a buffer layer, ahole transport layer, a light emitting layer, a hole blocking layer, anelectron transport layer (ETL), a cathode and a cap layer.

The anode is ITO, the thickness of the buffer layer is 10 nm, thethickness of the hole transport layer is 115 nm, the light emittinglayer is a blue light emitting layer and has a thickness of 25 nm, thethickness of the hole blocking layer is 20 nm, the thickness of theelectron transport layer is 35 nm, and the thickness of the cap layer is70 nm.

Specifically, the difference between the various organic light emittingdevices only lies in the following aspects.

The refractive index of the electron transport layer (ETL) of the firstorganic light emitting device Q1 is 1.70 at a wavelength of 550 nm, andthe constituent materials of the ETL includes ETL1

and Yb, ETL1:Yb=95:5, the material of the cathode is silver and itsthickness is 18 nm.

The refractive index of the electron transport layer (ETL) of the secondorganic light emitting device Q2 is 1.60 at a wavelength of 550 nm, andthe constituent materials of the ETL includes ETL1 and Yb,ETL1:Yb=25:75, the material of cathode is silver and its thickness is 18nm.

The refractive index of the electron transport layer (EFL) of the thirdorganic light emitting device Q3 is 1.65 at a wavelength of 550 nm, andthe constituent materials of the ETL includes ETL1 and Yb,ETL1:Yb=50:50, the material of cathode is silver and its thickness is 18nm.

The refractive index of the electron transport layer (ETL) of the fourthorganic light emitting device Q4 is 1.8 at a wavelength of 550 nm, andthe constituent materials of the ETL includes ETL2

the material of the cathode is a magnesium silver alloy (Mg:Ag=10:1) andits thickness is 15 nm.

After optical tests, the optical performances of Q1-Q4 are shown inTable 2 below:

Refractive index Light Color cast of of ETL@550 extraction efficiencyperspective@60° Q1 1.70 110% 95% Q2 1.60 115% 92% Q3 1.65 113% 95% Q41.8 100% 100%

Taking the organic light emitting display device as indicated by Q4 as acomparison example, the refractive index of Q1 is less than the one ofQ4, the light extraction efficiency of Q1 is increased to 110% withrespect to the one of Q4, and the color cast of Q1 is reduced to 95%with respect to the one of Q4. It is clear that the light extractionefficiency of Q1 is higher and the color cast thereof is less. That is,the organic light emitting display device as indicated by Q1 has abetter display effect.

Taking the organic light emitting display device as indicated by Q4 as acomparison example, the refractive index of Q2 is less than the one ofQ4, the light extraction efficiency of Q2 is increased to 115% withrespect to the one of Q4, and the color cast of Q2 is reduced to 92%with respect to the one of Q4. It is clear that the light extractionefficiency of Q2 is higher and the color cast thereof is less. That is,the organic light emitting display device as indicated by Q2 has abetter display effect.

Taking the organic light emitting display device as indicated by Q4 as acomparison example, the refractive index of Q3 is less than the one ofQ4, the light extraction efficiency of Q3 is increased to 113% withrespect to the one of Q4, and the color cast of Q3 is reduced to 95%with respect to the one of Q4. It is clear that the light extractionefficiency of Q3 is higher and the color cast thereof is less. That is,the organic light emitting display device as indicated by Q3 has abetter display effect.

The refractive index at wavelength of 550 nm is Q2<Q3<Q1<Q4.

It can be seen that the light extraction efficiency of the device can beimproved and the color cast can be reduced by way of reducing therefractive index of the electron transport layer and improving thematerial of the cathode, thereby improving the display effect of thedevice.

Yet another embodiment of the present disclosure provides yet anotherorganic light emitting display device which includes an anode, a bufferlayer, a hole transport layer, a light emitting layer, an electrontransport layer (ETL), a cathode and a cap layer (CPL).

The anode is ITO, the thickness of the buffer layer is 10 nm, thethickness of the hole transport layer is 115 nm, the light emittinglayer is a blue light emitting layer and its thickness is 25 nm, thethickness of the electron transport layer is 35 nm and its constituentmaterials includes ETL1

and Yb, the material of the cathode is silver and its thickness is 15nm, and the thickness of the cap layer is 70 nm.

Specifically, the difference between the various organic light emittingdevices only lies in the following aspects.

In the electron transport layer (ETL) of the first organic lightemitting display device Q1, ETL1:Yb=95:5, and the constituent materialsof the cap layer is ALQ3.

In the second organic light emitting display device Q2, ETL1:Yb=95:5,the cap layer includes a first cap layer and a second cap layer, theconstituent materials of the first cap layer is ALQ3 and its thicknessis 50 nm, and the constituent materials of the second cap layer is LiFand its thickness is 20 nm.

In the third organic light emitting display device Q3, ETL1:Yb=50:50,the cap layer includes a first cap layer and a second cap layer, theconstituent materials of the first cap layer is ALQ3 and its thicknessis 50 nm, and the constituent materials of the second cap layer is LiFand its thickness is 20 nm.

After optical tests, the optical performances of Q1-Q3 are shown inTable 3 below:

Light extraction ETL CPL efficiency Color cast@60° Q1 ETL1:Yb = 95:5ALQ3 100% 100% Q2 ETL1:Yb = 95:5 ALQ3/LiF 105% 90% Q3 ETL1:Yb = 50:50ALQ3/LiF 110% 80%

Taking the organic light emitting display device as indicated by Q1 as acomparison example, the cap layer of Q2 is of a double-film layerstructure, and the light extraction efficiency of Q2 is increased to105% with respect to the one of Q1, and the color cast of Q2 is reducedto 90% with respect to the one of Q1. It is clear that the lightextraction efficiency of Q2 is higher and its color cast is less. Thatis, the organic light emitting device as indicated by Q2 has a betterdisplay effect.

Taking the organic light emitting display device as indicated by Q1 as acomparison example, the cap layer of Q3 is of a double-film layerstructure, and the light extraction efficiency of Q3 is increased to110% with respect to the one of Q1, and the color cast of Q3 is reducedto 80% with respect to the one of Q1. It is clear that the lightextraction efficiency of Q3 is higher and its color cast is less. Thatis, the organic light emitting device as indicated by Q3 has a betterdisplay effect.

Among them, the difference between Q3 and Q2 lies in that the proportionof the constituent materials of the electron transport layer isdifferent, and the refractive index of ALQ3 is greater than that of LiF.It can be seen that the light extraction efficiency of the device can beimproved and its color cast can be reduced by improving the film layerstructure of the cap layer and the refractive index of each film layer,and by adjusting the constituent materials and material content of theelectron transport layer, thereby improving the display effect of thedevice.

The embodiment of the present disclosure also provides an organic lightemitting display apparatus which includes an organic light emittingdisplay device as described in any of the embodiments as describedabove. The organic light emitting display apparatus may be atop-emitting structure in which the light emitted from the lightemitting layer is emitted through one side surface of the secondelectrode.

According to the organic light emitting display apparatus of the presentembodiment, the light emitting layer may be formed of a color lightemitting material. For example, a first light emitting regioncorresponding to an R pixel region is formed of a red light emittingmaterial, a second light emitting region corresponding to a G pixelregion is formed of a green light emitting material, and a third lightemitting region corresponding to a B pixel region is formed of a bluelight emitting material. In other embodiments, however, the optionallight emitting layer is formed of a white light emitting material, andthe organic light emitting display apparatus further includes a redfilter film provided in correspondence with the first light emittingregion, and as a result, the white light emitted from the first lightemitting region forms red lights after passing through the red filterfilm; a green filter film is provided in correspondence with the secondlight emitting region, and as a result, the white light emitted from thesecond light emitting region form green lights after passing through thegreen filter film; and a blue filter film is provided in correspondencewith the third light emitting region, and as a result, the white lightemitted from the third light emitting region form blue lights afterpassing through the green filter film.

The organic light emitting display apparatus provided in the presentembodiment can be applied to a wearable smart bracelet or a displayfield such as a smart phone, a tablet computer and the like.

It is noted that the foregoing are only some embodiments of and thetechnical principles provided by the present disclosure. It will beunderstood by those skilled in the art that the present disclosure isnot limited to the specific embodiments described herein, and thatvarious changes, remodifications and substitutions will be madeapparently by those skilled in the art without departing from the scopeof the disclosure. Thus, while the present disclosure has been describedin more detail by way of the above embodiments, the present disclosureis not limited to the above embodiments, but may include more equivalentembodiments without departing from the concept of the presentdisclosure, and the scope of the present disclosure is to be determinedby the scope of the appended claims.

What is claimed is:
 1. An organic light emitting display device,comprising: a first electrode and a second electrode disposed oppositeto each other; a light emitting layer positioned between the firstelectrode and the second electrode; a cap layer positioned on a sidesurface of the second electrode facing away from the light emittinglayer, wherein the cap layer comprises at least two composite layers,wherein a refractive index of the composite layer of the at least twocomposite layers closer to the second electrode is greater than that ofthe other composite layer further away from the second electrode in arange of wavelength of 400 nm to 700 nm, and when light propagates inthe at least two composite layers, a light emission angle in the othercomposite layer of the at least two composite layers further away fromthe second electrode is greater than a light emission angle in thecomposite layer of the at least two composite layers closer to thesecond electrode; and a first functional layer comprising at least anelectron transport layer, wherein the electron transport layer islocated on a side surface of the second electrode facing to the lightemitting layer, a refractive index of the electron transport layer isless than 1.7 in the wavelength range of 400 nm to 700 nm, and athickness of the electron transport layer is greater than or equal to 30nm and less than or equal to 40 nm.
 2. The organic light emittingdisplay device according to claim 1, wherein a thickness of the caplayer is greater than or equal to 50 nm and less than or equal to 90 nm.3. The organic light emitting display device according to claim 1,wherein the cap layer comprises at least one or both of an organicmaterial and an inorganic material.
 4. The organic light emittingdisplay device according to claim 3, wherein the cap layer comprises afirst composite layer and a second composite layer stacked on the firstcomposite layer, the first composite layer is in direct contact with thesecond electrode, a refractive index of the first composite layer isgreater than 1.8 in the wavelength range of 400 nm to 700 nm, and arefractive index of the second composite layer is less than 1.7 in thewavelength range of 400 nm to 700 nm.
 5. The organic light emittingdisplay device according to claim 4, wherein a thickness of the firstcomposite layer is 50 nm and a thickness of the second composite layeris 20 nm.
 6. The organic light emitting display device according toclaim 4, wherein the first composite layer is 8-hydroxyquinolinealuminum and the second composite layer is lithium fluoride.
 7. Theorganic light emitting display device according to claim 1, wherein theelectron transport layer comprises an electron transporting materialdoped with a first guest material.
 8. The organic light emitting displaydevice according to claim 7, wherein the first guest material comprisesat least an alkali metal, an alkaline earth metal and a rare earthmetal; and the electron transport material comprises any one of ano-phenanthroline derivative or a substituted product thereof and abipyridine derivative or a substituted product thereof.
 9. The organiclight emitting display device according to claim 7, wherein a content ofthe first guest material in the electron transport layer is greater thanor equal to 5% and less than or equal to 95%.
 10. The organic lightemitting display device according to claim 1, wherein the firstfunctional layer further comprises: a hole blocking layer located at aside surface of the electron transport layer facing the light emittinglayer, a thickness of the hole blocking layer is in the range from 5 nmto 30 nm.
 11. The organic light emitting display device according toclaim 1, wherein the electron transport layer comprises at least a firstelectron transport layer and a second electron transport layer stackedin turn, and the second electron transport layer is located on a sidesurface of the second electrode facing the light emitting layer.
 12. Theorganic light emitting display device according to claim 11, wherein athickness of the first electron transport layer is 15 nm and a thicknessof the second electron transport layer is 20 nm.
 13. The organic lightemitting display device according to claim 1, wherein constituentmaterials of the second electrode comprises a metal material or a metalalloy material, and the constituent materials of the first electrodecomprises indium tin oxide (ITO) or indium zinc oxide (IZO); or, theconstituent materials of the second electrode comprises indium tin oxide(ITO) or indium zinc oxide (IZO), and the constituent materials of thefirst electrode comprises a metal material or a metal alloy material.14. The organic light emitting display device according to claim 13,wherein the metal material is silver, and the metal alloy material is asilver alloy having a silver content of more than 90%.
 15. The organiclight emitting display device according to claim 1, further comprising asecond functional layer located on a side surface of the first electrodefacing the light emitting layer, the second functional layer comprise atleast a hole transport layer.
 16. The organic light emitting displaydevice according to claim 1, further comprising a first substratelocated on a side surface of the first electrode facing away from thelight emitting layer, the first substrate is a rigid substrate or aflexible substrate.
 17. The organic light emitting display deviceaccording to claim 1, wherein the organic light emitting display deviceis a top-emitting display device.
 18. An organic light emitting displayapparatus comprising an organic light emitting display device,comprising: a first electrode and a second electrode disposed oppositeto each other; a light emitting layer positioned between the firstelectrode and the second electrode, and a cap layer positioned on a sidesurface of the second electrode facing away from the light emittinglayer, wherein the cap layer comprises at least two composite layers, arefractive index of the composite layer of the at least two compositelayers closer to the second electrode is greater than that of the othercomposite layer further away from the second electrode in a range ofwavelength of 400 nm to 700 nm, and when light propagates in the atleast two composite layers, a light emission angle in the compositelayer of the at least two composite layers further away from the secondelectrode is greater than a light emission angle in the composite layerof the at least two composite layers closer to the second electrode; anda first functional layer comprising at least an electron transportlayer, wherein the electron transport layer is located on a side surfaceof the second electrode facing to the light emitting layer, a refractiveindex of the electron transport layer is less than 1.7 in the wavelengthrange of 400 nm to 700 nm, and a thickness of the electron transportlayer is greater than or equal to 30 nm and less than or equal to 40 nm.